| With the development of wireless communication technology,antennas with good performance such as wide frequency bands,miniaturization,low cross-polarization levels,and stable radiation patterns are becoming more and more popular.Especially in the application of phased array antennas,having a wider frequency band means that it can be applied to more application fields,and having a smaller antenna element means that it can be widely used in various aircraft.Therefore,it is of great engineering significance to study array antenna elements with the characteristics of miniaturization in a wide frequency band.In the application of phased array antennas,microstrip printed dipole antennas are popular because of their low cost,light weight,and ease of installation and manufacturing.However,it is difficult for the conventional microstrip printed dipole antenna to obtain miniaturization,low cross-polarization level and stable radiation pattern simultaneously in a sufficiently wide frequency band.In this thesis,based on the traditional microstrip printed dipole antenna,the characteristics of its wide frequency band,miniaturization and low cross-polarization are studied in depth.The main work and research results of the paper are as follows:Firstly,broadband design based on microstrip printed dipole antenna.A microstrip printed dipole antenna with bilateral directors is designed.In order to improve its broadband characteristics,the antenna uses an impedance-transformed balun;the introduction of bilateral directors allows the antenna to obtain more stable radiation characteristics and further improve the impedance characteristics.The size of the antenna is 27×22×12mm~3,which achieves an impedance bandwidth of about 24.2%(8.1?10.1GHz),and obtained half-power beamwidths greater than 60°and 140°in the E-plane and H-plane,respectively.Then a microstrip printed dipole antenna with low cross-polarization level was designed.In order to reduce its cross-polarization level,the antenna adopts a double-sided printed dipole arm structure;by loading parasitic elements,the impedance bandwidth of the antenna is greatly expanded.The size of the antenna is 47×33×1.57mm~3,which achieves an impedance bandwidth of about 76.9%(2.4?5.4GHz),and cross-polarization levels greater than -40dB and-20dB are obtained in the E-plane and H-plane,respectively.Secondly,miniaturized broadband design based on microstrip printed dipole antenna.A broadband miniaturized microstrip printed dipole antenna is designed.By improving the coupling slot line as a stepped loading sector structure,and using the multi-level impedance transformation technology and the method of loading the fan shape at the feeding balun matching end,the broadband and miniaturization of the microstrip printed dipole antenna are realized.The size of the antenna is 19.5×14.6×0.47mm~3,which realizes an impedance bandwidth of about 40%(8?12GHz),and obtains half-power beamwidths greater than 60°and140°in the E-plane and H-plane,respectively.Then the antenna is formed into a 1×5array,and it is fed with a one-to-five unequal feed network.The size of the array is 120×67×15.7mm~3.The simulation results show that the antenna array gain?10.26dBi,H plane beam width>14.27°,E plane beam width>109.35°.Finally,the array is processed and tested,and the test results are consistent with the simulation results.Thirdly,low sidelobe design based on microstrip printed dipole antenna.A low-side lobe antenna array is designed,and the requirements of low side lobe are realized by using Taylor amplitude weighted distribution.The proposed antenna array is composed of a cascade of sixty-four unequal feed networks and antenna arrays.The antenna structure size is 1728×22×112.55mm~3.Simulation results show that antenna array gain?22dB,the beam width?1.3°and the SLL?-25dB,which meet the design index requirements.The integrated processing of the antenna array and the feed network is beneficial to reduce the errors generated during the installation process,and has certain practical value in engineering. |
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